1. Field of the Invention
The invention relates to an indicator for indicating the optimum angular position of a sail on a sailing vessel.
2. Description of the Prior Art
A device is known which may be used on sailing vessels for indicating the sail orientation which should provide the strongest thrust in the sailing direction of the vessel. The device operates on a principle based on an observation which will now be described.
If (A) is called the wind angle and (B) is called the sail angle, defined with respect to the axis of the vessel from stern to bow and being assigned a sign in accordance with the usual convention, the incidence angle of the wind on the sail is (A) - (B). The reaction force received by the sail, perpendicular to itself, is proportional to the sine of the angle (A) - (B). Thus, for a wind having a given force, the component of the reaction force in the sailing direction will be proportional to the product EQU sin {(A) - (B)}.times. sin(B)
A simple calculation will therefore show that this product reaches a maximum when (B) = (A)/2.
This prior art device comprises a vane type member which drives a pinion which in turn drives a second pinion having a diameter twice that of the first pinion, either directly or by means of an auxiliary pinion. Thus, the shaft of the second pinion turns at an angle equal to half that of the vane and in the same direction. A direction index or indicator as well as the entire device is mounted on the vessel and set such that for a following wind coaxial with the direction of displacement of the vessel {(A) = 180.degree.}, the indicator indicates an angular position of the sail perpendicular to the direction of displacement {(B) = 90.degree.}.
Using such an arrangement the vessel pilot could quickly adjust his sail so as to obtain the best possible thrust.
Unfortunately, such a device is based upon an overly simplified theory which is only valid for small or large wind angles but not for any intermediate values.